Novel 6XHE and 6XKY aluminum alloy flat cast ingot for automobile sheet and preparation method of sheet

Abstract

The invention provides a preparation method of a novel 6XHE and 6XKY aluminum alloy flat cast ingot for an automobile sheet, which comprises the following steps: A) proportioning aluminum alloy components, and smelting raw materials to obtain a smelted material; b) sequentially performing melt purification and online refining on the smelted material to obtain a purified product; c) casting the purified product to obtain a cast ingot; pure aluminum is adopted for bottoming in casting, the initial water flow rate of casting is 70-80% of the steady-state water flow rate, and the initial casting speed of casting is 36-39 mm / min; after casting is stable, the casting speed is 40-45 mm / min, the casting temperature is 720-735 DEG C, the casting water flow is 70-80 m < 3 > / h, the temperature of molten aluminum at the tail end of a flow table is 695-705 DEG C, and the water temperature is 20-25 DEG C. The problem that cast ingots are difficult to form is solved, and the obtained plate is good in strength and bending performance and good in ductility.

Description

Technical Field

[0001] This invention belongs to the field of metal smelting technology, and particularly relates to a method for preparing a novel 6XHE and 6XKY aluminum alloy flat casting ingot and sheet for automotive panels. Background Technology

[0002] As an ideal lightweight material, aluminum alloy sheets are increasingly used in automobiles, especially in new energy vehicles. With increasingly stringent environmental requirements, the aluminum used in automotive exterior panels is primarily 6-series alloy (Al-Mg-Si), while the aluminum used in interior panels is primarily 5-series alloy (Al-Mg). These are joined together through complex processes such as adhesive bonding and riveting, and their compositions differ significantly, making them difficult to recycle at the same level. Considering aluminum alloy recycling, replacing 5-series alloys with 6-series alloys for interior panels is a trend. However, 6-series alloys for interior panels require higher formability than exterior panels, and due to the presence of exposed surfaces, they also demand high surface quality.

[0003] 6XHE and 6XKY aluminum alloys belong to the Al-Mg-Si system of 6xxx aluminum alloys. As the impurity content decreases and the composition range narrows, the casting process window also narrows, and the difficulty of ingot forming increases significantly. Existing aluminum alloy melting and casting processing technologies are insufficient to guarantee the quality requirements of ingot forming and sheet performance. Summary of the Invention

[0004] The purpose of this invention is to provide a new method for preparing 6XHE and 6XKY aluminum alloy flat ingots and plates for automotive panels. The method in this invention solves the problem of the difficulty in forming 6XHE and 6XKY aluminum alloy ingots, and the obtained plates have good strength, bending performance and elongation.

[0005] This invention provides a method for preparing novel 6XHE and 6XKY aluminum alloy flat casting ingots for automotive steel sheets, comprising the following steps:

[0006] A) The aluminum alloy components are batched, and the raw materials are melted to obtain the melt;

[0007] B) The molten material is subjected to melt purification and online refinement in sequence to obtain a purified product;

[0008] C) Cast the purified product to obtain an ingot;

[0009] The casting process uses pure aluminum as the base, the initial water flow rate is 70-80% of the steady-state water flow rate, and the initial casting speed is 36-39 mm / min.

[0010] After the casting process stabilizes, the casting speed is 40-45 mm / min, the casting temperature is 720-735℃, and the casting water flow rate is 70-80 m³ / min. 3 / h / root, aluminum liquid temperature at the end of the flow plate 695~705℃, water temperature 20~25℃.

[0011] Preferably, the 6XHE aluminum alloy comprises the following components by mass fraction: Si: 0.74~0.86%, Fe: 0.20~0.25%, Cu: 0.05~0.10%, Mn: 0.13~0.17%, Mg: 0.22~0.28%, Cr: 0.06~0.10%, Ti: 0.015~0.025%, Zn≤0.10%, with the balance being Al;

[0012] 6XKY aluminum alloy comprises the following components by mass fraction: Si: 1.22~1.38%, Fe: 0.18~0.23%, Cu: 0.02~0.08%, Mn: 0.08~0.12%, Mg: 0.30~0.50%, Cr≤0.05%, Ti: 0.01~0.04%, Zn≤0.05%, with the balance being Al.

[0013] Preferably, the melting temperature in step A) is 720~760℃.

[0014] Preferably, the melt purification in step B) includes refining and online filtration;

[0015] In step B), the online grain refinement is performed using Al-5Ti-1B wire.

[0016] Preferably, in step C), the temperature of the molten aluminum at the bottom is 720~740℃, the bottom-laying speed is 34~36mm / min, and the molten material is added when the bottom-laying thickness reaches 50mm.

[0017] This invention provides a method for preparing novel 6XHE and 6XKY aluminum alloy sheets for automotive panels, comprising the following steps:

[0018] The 6XHE and 6XKY aluminum alloy flat ingots were sequentially milled, rolled, intermediate annealed, roughened and solution quenched to obtain new 6XHE and 6XKY aluminum alloy sheets for automotive panels.

[0019] The 6XHE and 6XKY aluminum alloy flat castings are novel 6XHE and 6XKY aluminum alloy flat castings for automotive panels prepared by the preparation method described in any one of claims 1 to 5.

[0020] The rolling process includes the following steps:

[0021] The milled ingot is first heated to 525~535℃, then heated to 545~555℃, and held at the second heating temperature for 7~9 hours. The ingot is then cooled in the furnace to 515~525℃ before being taken out of the furnace for hot rolling and cold rolling.

[0022] Preferably, the hot rolling process includes hot roughing and hot finishing. The hot roughing speed is 70-90 m / min, the initial rolling temperature is 510-530℃, and after hot roughing to a plate thickness of 30-38 mm, hot finishing is performed. The hot finishing temperature is 260-280℃, the hot finishing speed is 4-8 m / s, and after hot finishing to a plate thickness of 4.0-6.0 mm, cold rolling is performed to a plate thickness of 0.8-1.65 mm.

[0023] Preferably, the intermediate annealing temperature is 480~490℃, and the holding time is 20~40s.

[0024] Preferably, in the texturing step, the texturing reduction is 0.01~0.03mm and the elongation is 1.0~2.0%.

[0025] Preferably, the solution quenching temperature is 525~560℃, and the holding time is 20~40s.

[0026] This invention provides a method for preparing novel 6XHE and 6XKY aluminum alloy flat ingots for automotive sheet metal, comprising the following steps: A) batching aluminum alloy components and melting the raw materials to obtain a molten material; B) subjecting the molten material to melt purification and online refinement sequentially to obtain a purified product; C) casting the purified product to obtain an ingot; the casting uses pure aluminum as the base layer, the initial water flow rate is 70-80% of the steady-state water flow rate, and the initial casting speed is 36-39 mm / min; after the casting stabilizes, the casting speed is 40-45 mm / min, the casting temperature is 720-735℃, and the casting water flow rate is 70-80 m³ / min. 3 / h / root, aluminum liquid temperature at the end of the flow plate 695~705℃, water temperature 20~25℃.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] 1. This invention solves the problem of difficult ingot forming by developing a reasonable casting process.

[0029] 2. Through a reasonable sheet rolling process, the present invention obtains sheet materials with good strength, bending performance and elongation; the room temperature tensile strength in T63 state is in the range of 150~170 MPa, the room temperature yield strength is in the range of 70~80 MPa, the baked yield strength is in the range of 90~110 MPa, the baked tensile strength is in the range of 160~180 MPa, the maximum elongation is in the range of 23~27%, and there is no cracking when bent at 90°.

[0030] 3. This invention addresses the problem of the difficulty in recycling the inner and outer panels of automobiles at the same level, enabling them to be recycled simultaneously with the 6014 and 6016 alloys used in the outer panels of automobiles, making them easy to reuse.

[0031] 4. The preparation method provided by this invention is simple to operate, has good batch operation capability, high production efficiency, and does not increase manufacturing costs.

[0032] 5. The operation is simple and clear, and it is highly feasible on site. Detailed Implementation

[0033] This invention provides a method for preparing novel 6XHE and 6XKY aluminum alloy flat casting ingots for automotive steel sheets, comprising the following steps:

[0034] A) The aluminum alloy components are batched, and the raw materials are melted to obtain the melt;

[0035] B) The molten material is subjected to melt purification and online refinement in sequence to obtain a purified product;

[0036] C) Cast the purified product to obtain an ingot;

[0037] The casting process uses pure aluminum as the base, the initial water flow rate is 70-80% of the steady-state water flow rate, and the initial casting speed is 36-39 mm / min.

[0038] After the casting process stabilizes, the casting speed is 40-45 mm / min, the casting temperature is 720-735℃, and the casting water flow rate is 70-80 m³ / min. 3 / h / root, aluminum liquid temperature at the end of the flow plate 695~705℃, water temperature 20~25℃.

[0039] This invention preferably uses aluminum ingots of a certain purity and other raw materials with good uniformity to ensure that impurity elements such as Fe, Cu, Mn, Cr, V, and Ti are controlled at low levels. Specifically, in some embodiments of this invention, the invention uses primary aluminum ingots with an Al grade of 99.7 or higher, intermediate alloys, pure metals, and primary and secondary waste materials for batching, wherein the amount of new aluminum used is ≥40%, and the amount of secondary waste used is ≤20%.

[0040] In this invention, the 6XHE aluminum alloy comprises the following components by mass fraction: Si: 0.74~0.86%, Fe: 0.20~0.25%, Cu: 0.05~0.10%, Mn: 0.13~0.17%, Mg: 0.22~0.28%, Cr: 0.06~0.10%, Ti: 0.015~0.025%, Zn≤0.10%, with the balance being Al; the 6XKY aluminum alloy comprises the following components by mass fraction: Si: 1.22~1.38%, Fe: 0.18~0.23%, Cu: 0.02~0.08%, Mn: 0.08~0.12%, Mg: 0.30~0.50%, Cr≤0.05%, Ti The proportions are 0.01~0.04%, Zn≤0.05%, and the balance is Al. The ingredients can be prepared according to the composition of 6XHE aluminum alloy and 6XKY aluminum alloy. The details will not be elaborated here.

[0041] In this invention, the raw materials are prepared according to the aluminum alloy composition and then smelted to obtain the molten material.

[0042] In this invention, the temperature of the capacity is preferably 720~760℃, more preferably 730~750℃, such as 720℃, 725℃, 730℃, 735℃, 740℃, 745℃, 750℃, 755℃, 760℃, and preferably a range of values ​​with any of the above values ​​as the upper or lower limit.

[0043] After obtaining the molten material, the present invention sequentially performs melt purification and online refinement on the molten material to obtain a crystallized product.

[0044] In this invention, the melt purification includes refining and online filtration in sequence. The furnace uses Ar+Cl2 mixed gas for refining, and Ar is used for online refining. The melt filtration adopts plate filtration, and the filter plate is a domestic 40+50ppi filter plate that is used once.

[0045] In this invention, the online grain refinement is carried out using Al-5Ti-1B wire, with a preferred dosage of 1~1.5 kg / t, and more preferably 1.2~1.3 kg / t.

[0046] After obtaining the purified product, the present invention casts it. The present invention mainly solves the problem of the difficulty in forming 6XHE and 6XKY aluminum alloy ingots through the following four methods:

[0047] (1) Before casting, block 3 to 4 water holes on the edge of the crystallizer and set the initial water flow rate to 70 to 80% of the steady-state water flow rate to reduce the cooling intensity at the corner of the ingot and prevent cracking at the corner of the ingot.

[0048] (2) Before adding materials, use pure aluminum to lay the bottom. The temperature of the aluminum liquid for laying the bottom is preferably 720~740℃, more preferably 725~730℃. The laying speed is maintained at 34~36mm / min, more preferably 35mm / min. When the thickness of the bottom is 50mm, the hard shell and bottom slag on the surface are thoroughly cleaned before adding the base metal. At the same time, the cooling intensity is increased, and it is observed whether the aluminum and the base metal are well fused.

[0049] (3) When starting the machine, use high-speed casting, and maintain the casting speed at 36~39mm / min, preferably 37~38mm / min. Do not increase the casting speed to reduce aluminum leakage caused by excessive shrinkage or cold shut caused by low-speed start-up, and prevent aluminum leakage or cold shut from becoming crack sources.

[0050] (4) After the casting stabilizes, the casting speed is set to 40~45 mm / min, preferably 42~44 mm / min, such as 40 mm / min, 41 mm / min, 42 mm / min, 43 mm / min, 44 mm / min, 45 mm / min, preferably within the range of any of the above values ​​as the upper or lower limit; the casting temperature is 720~735℃, preferably 725~730℃; the casting water flow rate is preferably 70~80 m³ / min. 3 / h / root, e.g., 70 m 3 / h / root, 71 m 3 / h / root, 72 m 3 / h / root, 73 m 3 / h / root, 74 m 3 / h / root, 75 m 3 / h / root, 76 m 3 / h / root, 77 m 3 / h / root, 78 m 3 / h / root, 79 m 3 / h / root, 80 m 3 / h / root, preferably a range of values ​​with any of the above values ​​as the upper or lower limit; the aluminum liquid temperature at the end of the flow tray is preferably 695~705℃, more preferably 700~702℃, and the water temperature is 20~25℃.

[0051] This invention also provides a method for preparing novel 6XHE and 6XKY aluminum alloy sheets for automotive panels, comprising the following steps:

[0052] The 6XHE and 6XKY aluminum alloy flat castings mentioned above are sequentially milled, rolled, intermediate annealed, roughened and solution quenched to obtain new 6XHE and 6XKY aluminum alloy sheets for automotive panels.

[0053] The rolling process includes the following steps:

[0054] The milled ingot is first heated to 525~535℃, then heated to 545~555℃, and held at the second heating temperature for 7~9 hours. The ingot is then cooled in the furnace to 515~525℃ before being taken out of the furnace for hot rolling and cold rolling.

[0055] After obtaining the new type of 6XHE and 6XKY aluminum alloy flat ingots for automotive sheet metal, the present invention mills the ingots to remove surface defects. The preferred single-sided milling amount of the large surface of the ingot is ≥15mm.

[0056] The milled ingot is heated using an integrated homogenization heating process. The milled ingot is first heated to 525~535℃, then heated to 545~555℃, and held at the second heating temperature for 7~9 hours. The ingot is then cooled in the furnace to 515~525℃ before being taken out of the furnace for hot rolling and cold rolling.

[0057] Preferably, in some embodiments of the present invention, during the ingot heating process, the primary furnace gas temperature (heating furnace chamber temperature) is set at 620°C. When the metal temperature reaches 530°C, the secondary furnace gas temperature (heating furnace chamber temperature) is set at 560°C. After the metal temperature reaches 550°C, the holding time is calculated and the holding time is 8 hours. The metal is then rolled out of the furnace, and the required temperature for exiting the furnace is 520±10°C.

[0058] In this invention, the rolling process preferably includes hot roughing, hot finishing, and cold rolling in sequence. The hot roughing speed is preferably 70-90 m / min, more preferably 75-85 m / min, such as 70 m / min, 75 m / min, 80 m / min, 85 m / min, 90 m / min, preferably within the range of any of the above values ​​as the upper or lower limit. The initial rolling temperature of the hot roughing is 510-530℃, more preferably 520-525℃. After hot roughing to a plate thickness of 30-38 mm, hot finishing is performed. The temperature of the hot finishing is preferably 260-280℃, more preferably 265-275℃, such as 260℃, 265℃, 270℃, 275℃, 280℃, preferably within the range of any of the above values ​​as the upper or lower limit. The hot finishing speed is 4-8 m / s, more preferably 5-7 m / s. The sheet is hot-rolled to a thickness of 4.0~6.0 mm and then cold-rolled to a thickness of 0.8~1.65 mm. During the cold rolling process, the cold rolling deformation rate is preferably 50~75%, more preferably 60~75%.

[0059] In this invention, the cold-rolled product coil is subjected to intermediate annealing in an air cushion furnace. The intermediate annealing temperature is preferably 480~490℃, more preferably 485~490℃; the intermediate annealing holding time is preferably 20~40s, more preferably 30~35s; the unit operating speed is preferably 10~15 meters / minute; and the pressure of the upper and lower water spray groups is set to 0.2 bar.

[0060] In this invention, the product roll after intermediate annealing is roughened by a 2800mm cold rolling mill. The roughening reduction is preferably 0.01~0.03mm and the elongation is preferably 1.0~2.0%.

[0061] The present invention involves solution quenching the roughened product roll in an air cushion furnace. During the solution quenching process, the solution temperature is preferably controlled at 525~560℃, more preferably at 530~550℃, such as 525℃, 530℃, 535℃, 540℃, 545℃, 550℃, 555℃, 560℃, preferably within the range of any of the above values ​​as the upper or lower limit. The holding time is preferably 20~40s, more preferably 30s, and the unit operating speed is 20~35 meters / minute.

[0062] This invention provides a method for preparing novel 6XHE and 6XKY aluminum alloy flat ingots for automotive sheet metal, comprising the following steps: A) batching aluminum alloy components and melting the raw materials to obtain a molten material; B) subjecting the molten material to melt purification and online refinement sequentially to obtain a purified product; C) casting the purified product to obtain an ingot; the casting uses pure aluminum as the base layer, the initial water flow rate is 70-80% of the steady-state water flow rate, and the initial casting speed is 36-39 mm / min; after the casting stabilizes, the casting speed is 40-45 mm / min, the casting temperature is 720-735℃, and the casting water flow rate is 70-80 m³ / min. 3 / h / root, aluminum liquid temperature at the end of the flow plate 695~705℃, water temperature 20~25℃.

[0063] Compared with the prior art, the present invention has the following advantages:

[0064] 1. This invention solves the problem of difficult ingot forming by developing a reasonable casting process.

[0065] 2. Through a reasonable sheet rolling process, the present invention obtains sheet materials with good strength, bending performance and elongation; the room temperature tensile strength in T63 state is in the range of 150~170 MPa, the room temperature yield strength is in the range of 70~80 MPa, the baked yield strength is in the range of 90~110 MPa, the baked tensile strength is in the range of 160~180 MPa, the maximum elongation is in the range of 23~27%, and there is no cracking when bent at 90°.

[0066] 3. This invention addresses the problem of the difficulty in recycling the inner and outer panels of automobiles at the same level, enabling them to be recycled simultaneously with the 6014 and 6016 alloys used in the outer panels of automobiles, making them easy to reuse.

[0067] 4. The preparation method provided by this invention is simple to operate, has good batch operation capability, high production efficiency, and does not increase manufacturing costs.

[0068] 5. The operation is simple and clear, and it is highly feasible on site.

[0069] To further illustrate the present invention, the following describes in detail, with reference to embodiments, a method for preparing a novel 6XHE and 6XKY aluminum alloy flat casting ingot and sheet metal for automotive panels provided by the present invention, but this should not be construed as limiting the scope of protection of the present invention.

[0070] Example 1

[0071] Ingot dimensions: 510×2020mm;

[0072] Batching process: Batching is carried out according to the alloy composition, using Al99.70 aluminum ingots, 6061, 6101, 4004 first-grade scrap (proportion 45%), intermediate alloys and metals;

[0073] Melting process: After the alloy raw materials are completely melted, samples are taken for analysis; the melting temperature in the furnace is 740±10℃;

[0074] Melt purification: Ar+Cl2 mixed gas is used for refining in the furnace, Ar is used for online refining, and plate filter is used for melt filtration. The filter plate is a domestic 40+50ppi and can be used once.

[0075] Online grain refinement: Al-5Ti-1B wire is used for online grain refinement at a dosage of 1.2 kg / t;

[0076] Casting parameters: molten aluminum temperature at the end of the casting plate: 697℃; casting speed: 42mm / min; initial water flow rate: 65m³ / min. 3 / h / root, steady-state water flow rate is 75m³ / h 3 / h / piece; cooling water temperature 27℃; both castings are qualified.

[0077] Ingot inspection:

[0078] (1) Low magnification of ingots: grain size grade 1.5; the test method is GB / T3246.2 "Methods for testing the microstructure of wrought aluminum and aluminum alloy products - Part 2: Methods for testing the microstructure of low magnification";

[0079] (2) Hydrogen content: 0.101 ml / 100 g Al; the detection method is YS / T600 "Method for determination of hydrogen in liquid aluminum and aluminum alloys - closed-loop circulation method".

[0080] Milling of ingot edges: Mill off 15mm from both the top and bottom of the large surface of the ingot;

[0081] Ingot heating: The primary furnace gas is kept at a constant temperature of 620℃. When the metal temperature reaches 530℃, the secondary furnace gas is kept at a constant temperature of 560℃. When the metal temperature reaches 550℃, the holding time is calculated and the holding time is 8 hours. After the metal is removed from the furnace and rolled, the metal temperature is required to be 520±10℃.

[0082] Plate rolling: Rough rolling temperature 520℃, rolling speed 75mm / min, rolling 10 times to 32±1mm and then finishing rolling, the final rolling temperature needs to be controlled at 270±10℃, rolling 4 times to 4±1mm and then cold rolling, deformation rate 50%, cold rolling to 0.92mm, deformation rate 75% during cold rolling;

[0083] Intermediate annealing: The cold-rolled product coil is subjected to intermediate annealing in an air cushion furnace. During the intermediate annealing process, the temperature is controlled at 490℃, the holding time is 30 seconds, the unit running speed is 11 meters / minute, and the pressure of the upper and lower water spray is set to 0.2 bar.

[0084] Textured rolling: The cold-rolled product coil is textured using a 2800mm cold rolling mill, with a textured reduction of 0.02mm and an elongation of 2.0%.

[0085] Solution quenching: When the sheet metal is in T63 condition, the cold-rolled product coil is solution quenched; during the solution quenching process, the solution temperature is controlled at 530℃, the initial holding temperature is 527℃, the holding time is 30 seconds, and the unit operating speed is 33 meters / minute.

[0086] Performance testing: room temperature yield strength 78 MPa, room temperature tensile strength 169 MPa, elongation 25%, baked yield strength 105 MPa, baked room temperature tensile strength 174 MPa, 90-degree bending test passed.

[0087] Example 2

[0088] Ingot dimensions: 510×2020mm;

[0089] Batching process: Batching is carried out according to the alloy composition, using Al99.70 aluminum ingots, 6A02, 4004 grade 1 scrap (proportion 45%), intermediate alloy and metal ingredients;

[0090] Melting process: After the alloy raw materials are completely melted, samples are taken for analysis; the melting temperature in the furnace is 740±10℃;

[0091] Melt purification: Ar+Cl2 mixed gas is used for refining in the furnace, Ar is used for online refining, and plate filter is used for melt filtration. The filter plate is domestic 40+50ppi and can be used twice.

[0092] Online grain refinement: Al-5Ti-1B wire is used for online grain refinement at a dosage of 1.2 kg / t;

[0093] Casting parameters: molten aluminum temperature at the end of the casting plate: 700℃; casting speed: 43mm / min; initial water flow rate: 65m³ / min. 3 / h / root, steady-state water flow rate is 76m³ / h 3 / h / piece; cooling water temperature 26℃; both castings are qualified.

[0094] Ingot inspection:

[0095] (1) Low magnification of ingots: grain size grade 1.5; the test method is GB / T3246.2 "Methods for testing the microstructure of wrought aluminum and aluminum alloy products - Part 2: Methods for testing the microstructure of low magnification";

[0096] (2) Hydrogen content: 0.108 ml / 100 g Al; the detection method is YS / T600 "Method for determination of hydrogen in liquid aluminum and aluminum alloys - closed-loop circulation method".

[0097] Milling the edges of the ingot: Mill off 17mm from both the top and bottom surfaces of the ingot.

[0098] Ingot heating: The primary furnace gas is kept at a constant temperature of 620℃. When the metal temperature reaches 530℃, the secondary furnace gas is kept at a constant temperature of 560℃. When the metal temperature reaches 550℃, the holding time is calculated and the holding time is 8 hours. After the metal is removed from the furnace and rolled, the metal temperature is required to be 520±10℃.

[0099] Plate rolling: Rough rolling temperature 520℃, rolling speed 75mm / min, rolling 10 times to 32±1mm and then finishing rolling, the final rolling temperature needs to be controlled at 270±10℃, rolling 4 times to 4±1mm and then cold rolling, deformation rate 50%, cold rolling to 0.92mm, deformation rate 75% during cold rolling;

[0100] Intermediate annealing: The cold-rolled product coil is subjected to intermediate annealing in an air cushion furnace. During the intermediate annealing process, the temperature is controlled at 490℃, the holding time is 30 seconds, the unit running speed is 11 meters / minute, and the pressure of the upper and lower water spray is set to 0.2 bar.

[0101] Textured rolling: The cold-rolled product coil is textured using a 2800mm cold rolling mill, with a textured reduction of 0.02mm and an elongation of 2.0%.

[0102] Solution quenching: When the sheet metal is in T63 condition, the cold-rolled product coil is solution quenched; during the solution quenching process, the solution temperature is controlled at 530℃, the initial holding temperature is 527℃, the holding time is 30 seconds, and the unit operating speed is 33 meters / minute.

[0103] Performance testing: room temperature yield strength 77 MPa, room temperature tensile strength 167 MPa, elongation 24.5%, baked yield strength 109 MPa, baked room temperature tensile strength 174 MPa, 90-degree bending test passed.

[0104] Example 3

[0105] Aluminum alloys are prepared according to the following method: batching, melting, melt purification, grain refinement and casting, milling, rolling, intermediate annealing, texturing, and solution quenching are performed sequentially.

[0106] Ingot dimensions: 510x2020mm;

[0107] Batching process: Batching is carried out according to the alloy composition, using Al99.70 aluminum ingots, 6061 and 4004 first-grade scrap (proportion 42%), intermediate alloys and metals;

[0108] Smelting process: After the alloy raw materials are completely melted, samples are taken for analysis; the melting temperature in the furnace is 720~760℃;

[0109] Melt purification: Ar+Cl2 mixed gas is used for refining in the furnace, Ar is used for online refining, and plate filter is used for melt filtration. The filter plate is a domestic 40+50ppi and can be used once.

[0110] Online grain refinement: Al-5Ti-1B wire is used for online grain refinement at a dosage of 1.2 kg / t;

[0111] Casting parameters: molten aluminum temperature at the end of the casting plate 703℃; casting speed 42mm / min; initial water flow rate 65m³ / min. 3 / h / root, steady-state water flow rate is 75m³ / h 3 / h / piece; cooling water temperature 26℃; both castings are qualified.

[0112] Ingot inspection:

[0113] (1) Low magnification of ingots: grain size grade 1.5; the test method is GB / T3246.2 "Methods for testing the microstructure of wrought aluminum and aluminum alloy products - Part 2: Methods for testing the microstructure of low magnification";

[0114] (2) Hydrogen content: 0.104 ml / 100 g Al; the detection method is YS / T600 "Method for determination of hydrogen in liquid aluminum and aluminum alloys - closed-loop circulation method".

[0115] Milling the edges of the ingot: Mill off 17mm from both the top and bottom surfaces of the ingot.

[0116] Ingot heating: First furnace gas is kept at a constant temperature of 620℃. When the metal temperature reaches 530℃, the furnace gas is switched to a constant temperature of 560℃. When the metal temperature reaches 550℃, the holding time is calculated and is 8 hours. After the metal is removed from the furnace and rolled, the metal temperature is required to be 520±10℃.

[0117] Plate rolling: Rough rolling temperature 520℃, rolling speed 75mm / min, rolling 10 passes to 36±1mm and then finishing rolling, the final rolling temperature needs to be controlled at 270±10℃, rolling 4 passes to 6±1mm and then cold rolling to 1.62mm, the deformation rate during cold rolling is 60%;

[0118] Intermediate annealing: The cold-rolled product coil is subjected to intermediate annealing in an air cushion furnace. During the intermediate annealing process, the temperature is controlled at 490℃, the holding time is 30 seconds, the unit operating speed is 14 meters / minute, and the pressure of the upper and lower water spray is set to 0.2 bar.

[0119] Texturing: The cold-rolled product coil is texturized by a 2800mm cold rolling mill with a texturing reduction of 0.02mm and an elongation of 2.0%.

[0120] Solution quenching: When the sheet metal is in T63 condition, the cold-rolled product coil is solution quenched; during the solution quenching process, the solution temperature is controlled at 555℃, the holding time is 30 seconds, and the unit operating speed is 21 meters / minute.

[0121] Performance testing: room temperature yield strength 75 MPa, room temperature tensile strength 165 MPa, elongation 25%, baked yield strength 99 MPa, baked room temperature tensile strength 164 MPa, 90-degree bending test passed.

[0122] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a novel 6XHE and 6XKY aluminum alloy flat casting ingot for automotive sheet metal, comprising the following steps: A) The aluminum alloy components are batched, and the raw materials are melted to obtain the melt; B) The molten material is subjected to melt purification and online refinement in sequence to obtain a purified product; C) Cast the purified product to obtain an ingot; The casting process uses pure aluminum as the base, the initial water flow rate is 70-80% of the steady-state water flow rate, and the initial casting speed is 36-39 mm / min. After the casting process stabilizes, the casting speed is 40-45 mm / min, the casting temperature is 720-735℃, and the casting water flow rate is 70-80 m³ / min. 3 / h / root, aluminum liquid temperature at the end of the flow plate 695~705℃, water temperature 20~25℃.

2. The method for preparing the novel 6XHE and 6XKY aluminum alloy flat casting ingots for automotive sheet metal according to claim 1, characterized in that, 6XHE aluminum alloy comprises the following components by mass fraction: Si: 0.74~0.86%, Fe: 0.20~0.25%, Cu: 0.05~0.10%, Mn: 0.13~0.17%, Mg: 0.22~0.28%, Cr: 0.06~0.10%, Ti: 0.015~0.025%, Zn≤0.10%, with the balance being Al; 6XKY aluminum alloy comprises the following components by mass fraction: Si: 1.22~1.38%, Fe: 0.18~0.23%, Cu: 0.02~0.08%, Mn: 0.08~0.12%, Mg: 0.30~0.50%, Cr≤0.05%, Ti: 0.01~0.04%, Zn≤0.05%, with the balance being Al.

3. The method for preparing the novel 6XHE and 6XKY aluminum alloy flat casting ingots for automotive sheet metal according to claim 1, characterized in that, The melting temperature in step A) is 720~760℃.

4. The method for preparing the novel 6XHE and 6XKY aluminum alloy flat casting ingots for automotive panels according to claim 1, characterized in that, The melt purification in step B) includes refining and online filtration; In step B), the online grain refinement is performed using Al-5Ti-1B wire.

5. The method for preparing the novel 6XHE and 6XKY aluminum alloy flat casting ingots for automotive sheet metal according to claim 1, characterized in that, In step C), the temperature of the molten aluminum at the bottom is 720~740℃, the bottom-laying speed is 34~36mm / min, and when the bottom-laying thickness reaches 50mm, the molten material is added.

6. A method for preparing a novel 6XHE and 6XKY aluminum alloy sheet for automotive applications, comprising the following steps: The 6XHE and 6XKY aluminum alloy flat ingots were sequentially milled, rolled, intermediate annealed, roughened and solution quenched to obtain new 6XHE and 6XKY aluminum alloy sheets for automotive panels. The 6XHE and 6XKY aluminum alloy flat castings are novel 6XHE and 6XKY aluminum alloy flat castings for automotive panels prepared by the preparation method described in any one of claims 1 to 5. The rolling process includes the following steps: The milled ingot is first heated to 525~535℃, then heated to 545~555℃, and held at the second heating temperature for 7~9 hours. The ingot is then cooled in the furnace to 515~525℃ before being taken out of the furnace for hot rolling and cold rolling.

7. The method for preparing novel 6XHE and 6XKY aluminum alloy sheets for automotive panels according to claim 6, characterized in that, The hot rolling process includes hot roughing and hot finishing. The hot roughing speed is 70-90 m / min, the initial rolling temperature is 510-530℃, and after hot roughing to a plate thickness of 30-38 mm, hot finishing is performed. The hot finishing temperature is 260-280℃, the hot finishing speed is 4-8 m / s, and after hot finishing to a plate thickness of 4.0-6.0 mm, cold rolling is performed to a plate thickness of 0.8-1.65 mm.

8. The method for preparing novel 6XHE and 6XKY aluminum alloy sheets for automotive panels according to claim 6, characterized in that, The intermediate annealing temperature is 480~490℃, and the holding time is 20~40s.

9. The method for preparing novel 6XHE and 6XKY aluminum alloy sheets for automotive panels according to claim 6, characterized in that, In the texturing step, the texturing reduction is 0.01~0.03mm, and the elongation is 1.0~2.0%.

10. The method for preparing novel 6XHE and 6XKY aluminum alloy sheets for automotive panels according to claim 6, characterized in that, The solution quenching temperature is 525~560℃, and the holding time is 20~40s.